Effects of T-activin on the morphology of the thymus gland in experimental injury of the lower limbs in mice (anti-stress effect of T-activin)

The effect of T-activin on thymic involution under the experimental trauma of femur was studied. T-activin in a dose of 1.0 micrograms/mouse was injected into young male (CBA X C57BL)F1 mice weighing 17.5-19.0 g before (I injection) or immediately after the fracture of the femur during 3 days. Morphometric analysis of the thymus was made 1, 5, 10 and 15 days after the trauma. It was found that T-activin suppressed the involution of the thymus, induced by the trauma, during the first 5 days and accelerate the process of its regeneration. It is suggested, that T-activin displays protective anti-stress effect on the mouse thymic involution.     

Elective detection of thymus epithelium and assessment of the degree of functional and pathological involution of the organ in mice

With the help of antibodies-containing serum reacting with the thymus reticulum epithelial cells components by immunofluorescence method the thymus parenchimal tissue in mice with functional and pathological involution has been detected electively. In spite of large thymus changes in hairless mice with the mutation of gene hrrhy in 14-th chromosome of B10.R109/Y animals the basal cells antigen in epithelial reticulum has been preserved. It permits to estimate thymus involution level of this organ. Low lymphocyte content in the thymus of C57BL/6 mice is accompanied by total decamouflage of the epithelium. The functional thymus involution of pregnant mice is characterized by the luminescence of large number of epithelial cells, the restoration of organ after the delivery--by their few number. The elective detection of thymus epithelium many serve as additional test for the estimation of functional and pathological involution level.     

Effect of T-activin on thymocyte reproduction and migration

Forty seven F1 (CBA X C57Bl) mice were used for quantitative morphologic examination of the thymus on 1, 5, 10 and 15 days after a single injection of 0.5 microgram T-activin, and injections of 0.1 microgram of T-activin once a day during 5 days. The number of transformed thymocytes and mitoses figures in cortex was found to be increased reaching a maximum at the 5th day as regards the magnitude and spreading. By the end of the research the number of transformed thymocytes and mitoses returned to initial values. There was a periodical (at the 5th and 10th days) 1 mm2 reduction in the number of thymocytes, an increase in the proportion of medullary thymocytes, reaching maximum at the 5th day, and a tendency towards the reduction of a relative area of the parenchyma. These indicators did not return to the initial values by the 15th days. However there was a tendency towards normalization. The conclusion is made about the stimulatory effect of T-activin on reproduction and migration of thymocytes.     

Change in immunological and biochemical parameters in germ-free animals in response to T-activin

The influence of immunoregulating humoral thymus factor T-activin (fraction AFT-6) on the activity of xenobiotic metabolism enzymes (EMX) and cellular-dependent cytotoxicity was investigated in germ-free guinea-pigs. Germ-free and conventional animals were injected 5 micrograms of T-activin intraperitoneally, on 3 successive days. The control animals were injected a physiologic saline. A day after the last injection the animals were killed, and EMX and K cell activity was measured. It was found that EMX activity in germ-free animals was decreased. T-activin stimulated cytochrome P-450, NADP-cytochrome-C-reductase, glutathione-S-transferase, benzopyrene hydroxylase and epoxyhydrase activity. In conventional animals the activity of these enzymes remained unchanged under the influence of T-activin. K-cell activity in germ-free animals was decreased, as compared to conventional guinea-pigs. Under the influence of T-activin the parameter increased and stood at about 70% of normal values.     

Cell proliferation in mouse tissues after thymectomy and the administration of T-activin

The epithelium of mouse cornea and lymph nodes was examined for DNA-synthetic and mitotic activity at different times after thymectomy and administration of T-activin, an active factor of the thymus. Thymectomy entails retardation of the rate of corneal epithelium regeneration, diminution in both tissues under study of the amplitude of oscillations in cell proliferation throughout the day. Administration to the animals of the immunoactive thymic factor T-activin makes the circadian rhythm of cell proliferation return to normal. It is assumed that T-activin raises the capacity of lymphocytes to interact with epithelial cells, which manifests itself in the enhancement of their mitotic activity.     

Morphometrical analysis of the thymus from mice submitted to low temperature

Thymic involution is a slow physiological process than can be accelerated by some pathological or experimental conditions. In this work we kept male mice under low temperatures in order to observe whether or not thymic involution would be promoted. For this purpose, we carried out a histometrical analysis of the thymus and observed that there was a decrease in both cortical and medullary regions of the thymic lobules. These changes paralleled a loss in the absolute and relative weights of the thymus. It was concluded that low temperatures induce thymic involution even in nonhibernating animals.     

Interaction of T-activin with peritoneal macrophages

The action of T-activin on peritoneal macrophages of CBA mice after its introduction into the animals has been studied. In intact mice the phagocytic activity of macrophages and their resistance to the cytopathogenic action of Salmonella typhimurium live cells remains unchanged. The injection of corpuscular pertussis vaccine into mice leads to a decrease in the resistance of macrophages to the action of salmonellae. The simultaneous injection of T-activin into mice in doses of 0.1 and 1.0 microgram per animal abolishes the damaging action of the vaccine. The analysis of the in vitro action of T-activin on macrophages of intact mice revealed that the preliminary incubation of cells with the preparation sharply increases their resistance to the action of salmonellae, while its introduction simultaneously with bacteria or after them rapidly leads to the death of macrophages. The action of T-activin is supposed to be linked with triggering the biosynthetic processes mediating the resistance of macrophages to the cytopathogenic action of salmonellae.     

Failure of rearranged TCR transgenes to prevent age-associated thymic involution.

After puberty, the thymus undergoes a dramatic loss in volume, in weight and in the number of thymocytes, a phenomenon termed age-associated thymic involution. Recently, it was reported that age-associated thymic involution did not occur in mice expressing a rearranged transgenic (Tg) TCRalphabeta receptor. This finding implied that an age-associated defect in TCR rearrangement was the major, if not the only, cause for thymic involution. Here, we examined thymic involution in three other widely used MHC class I-restricted TCRalphabeta Tg mouse strains and compared it with that in non-Tg mice. In all three TCRalphabeta Tg strains, as in control mice, thymocyte numbers were reduced by approximately 90% between 2 and 24 mo of age. The presence or absence of the selecting MHC molecules did not alter this age-associated cell loss. Our results indicate that the expression of a rearranged TCR alone cannot, by itself, prevent thymic involution. Consequently, other presently unknown factors must also contribute to this phenomenon.     

Effect of T-activin on the formation of conditioned reflex and manifestations of unconditioned reflex of avoidance in August strain rats]

It has been revealed that intraperitoneal injection of T-activin (humoral factor of the thymus) to August rats leads to more rapid and stable conditioned reflex formation to a sound and to a decrease of avoidance time when electric current is given to a shuttle chamber. Furthermore, less amount of uneffective series in testing unconditioned avoidance is registered in the test animals. A positive T-activin effect on conditioned reflex formation and unconditioned reflex manifestation is probably connected with its ability to alter hippocampus functional parameters and (or) with anti-stressor properties of the preparation.     

In vivo effect of progesteron and estrogen on thymus mass and T-cell functions in female mice

Progesteron and estradiol, administered in doses equivalent to those used for therapy caused a marked transient reduction of the thymus mass, but did not affect the cellularity of other lymphoid organs. Humoral and cellular immune response of the hormone-treated mice was normal at the time of thymus involution. The same was true for the stem-cell differentiation capacity. The remaining thymus cells after hormone treatment showed increased DNA-synthesis.     

Indomethacin inhibits thymic involution in mice with streptozotocin-induced diabetes

Diabetes is chronic disease that is accompanied by a rapid thymus involution. To investigate the factors responsible for thymic involution in a model of STZ-induced diabetes, mice were injected with STZ alone or in combination with the cyclooxygenase 2 inhibitor indomethacin (INDO). Thymus weight, glycemia and serum corticosterone were measured, and apoptosis in thymus and thymocyte cultures was analyzed by flow cytometry. Although earlier studies report that streptozotocin (STZ) is toxic to lymphoid tissues, in our experiments even massive doses of STZ did not negatively affect thymocyte cultures. Cultured thymocytes also seemed unaffected by high glucose concentrations, even after 24 h of exposure. Administration of INDO concomitantly with STZ reduced thymic involution but did not prevent the onset of hyperglycemia or reduce established hyperglycemia. When INDO was given before STZ, the same degree of thymic involution occurred; however, hyperglycemia was reduced, although normoglycemia was not restored. INDO also reduced serum corticosterone. Because thymocytes are known to be sensitive to glucocorticoids, this finding suggests that cyclooxygenase 2 inhibition may retard thymic involution by reducing serum glucocorticoids. In conclusion, our results show that STZ and hyperglycemia are not toxic to thymocytes and that cyclooxygenase 2-mediated mechanisms are involved in thymic involution during diabetes.     

Immunochemical identification and study of interspecies thymus antigen-2

A new interspecific animal thymus antigen (AgT-2) was identified. It was shown that AgT-2 is a microglobulin with a molecular mass about 12 kDa, electrophoretic mobility of alpha 1-globulins and isoelectric point of 4.6. Heating of the protein to 80 degrees C for 30 min did not lead to the loss of its immunochemical activity. AgT-2 was identified in extracts of bovine fetal thymus, spleen and liver. It was discovered in the extracts of the lung and colon of adult animals. Cross-reactions were found between bovine, walrus, deer and chicken AgT-2. This fact confirms that AgT-2 is interspecies-specific. AgT-2 was not identified in men, dogs, mice, rats and rabbits. Immunochemical research of immunocorrecting preparations revealed that AgT-2 is a constant component of T-activin, thymalin, thymosin and TP1-Serono and its concentration varies from 1.6 to 3.2%. It has been stated that immunochemical test for AgT-2 can be used as a marker in the production and standardization of active thymus factors.     

Effects of T-activin in viral myocarditis in animal experiments

The efficacy of immunomodulating agent T-activin has been studied in adult BALB/C mice infected with Coxsackie B1 virus. Optical, electron microscopic and immunological tests have shown that T-activin protects myocardium and modulates immune disorders in mice with viral myocarditis.     

The migration of bone marrow cells to thymic culture supernatants is inhibited by stress

The effect of immobilization stress on precursor cell migration from bone marrow to the thymus was studied in C57BL/6 mice. The in vitro migration assays, using Nuclepore chambers, showed that precursor cell migration to thymus supernatants was strongly inhibited in stressed animals. This inhibition of migration seemed to be cell-associated what can explain the thymic involution observed in mice under stress conditions. The migration of precursor cells from bone marrow may be one of the mechanisms by which the thymus gland is involuted by stress.     

The initial age-associated decline in early T-cell progenitors reflects fewer pre-thymic progenitors and altered signals in the bone marrow and thymus microenvironments

Age-related thymus involution results in decreased T-cell production, contributing to increased susceptibility to pathogens and reduced vaccine responsiveness. Elucidating mechanisms underlying thymus involution will inform strategies to restore thymopoiesis with age. The thymus is colonized by circulating bone marrow (BM)-derived thymus seeding progenitors (TSPs) that differentiate into early T-cell progenitors (ETPs). We find that ETP cellularity declines as early as 3 months (3MO) of age in mice. This initial ETP reduction could reflect changes in thymic stromal niches and/or pre-thymic progenitors. Using a multicongenic progenitor transfer approach, we demonstrate that the number of functional TSP/ETP niches does not diminish with age. Instead, the number of pre-thymic lymphoid progenitors in the BM and blood is substantially reduced by 3MO, although their intrinsic ability to seed and differentiate in the thymus is maintained. Additionally, Notch signaling in BM lymphoid progenitors and in ETPs diminishes by 3MO, suggesting reduced niche quality in the BM and thymus contribute to the early decline in ETPs. Together, these findings indicate that diminished BM lymphopoiesis and thymic stromal support contribute to an initial reduction in ETPs in young adulthood, setting the stage for progressive age-associated thymus involution.     

Nonspecific immunomodulation influences resistance of mice to experimental infection with Mesocestoides corti and Ascaris suum

The influence of nonspecific immunomodulation on the course of experimental infection was examined in larval cestodosis (Mesocestoides corti) and ascaridosis (Ascaris suum) in mice. Immunosuppressive treatment (with azathioprine or hydrocortisone) resulted in a decrease of resistance in both models. The subsequent administration of T-activin to immunosuppressed mice led to the restoration of resistance to a level equal to that of untreated control mice. The administration of different immunomodulators partially protected mice against M. corti (T-activin, thymomodulin) or A. suum (T-activin, thymomodulin, thymosin fr.5, bursa-activin) infection. The protective effect of different treatments did not correlate with the level of specific antibody in the sera of infected mice. These results, which confirmed the decisive role of T-cell immunity in the resistance to the helminth infections, raise the possibility of the use of immunomodulators (thymic preparations) in the immunoprophylaxis of helminthoses.     

Thymus, peripheral lymphoid tissues and immunological responsiveness of the pituitary dward mouse (author's transl)]

Snell's pituitary dwarf mice (dw) were used for studies on the relationship between hypophysis and lymphoid organs. The age-dependent changes of thymus or spleen weights of dwarf mice were compared with those of normal littermates. The suppression of growth of the thymus or spleen in dwarf mice was recognized at 5th day of age. Although involution of the thymus varied among animals, a strong positive correlation was demonstrated between relative thymus weight and body weight in 30 approximately 40 days old dwarf mice. Lymphoid organs of dwarf mice were reconstituted by injection of growth hormone and or thyroxin. Relative thymus weight significantly increased in dwarf mice when the treatment with growth hormone started at 7 days of age, but the same treatment at 3 months of age did not show any effect on the increment of relative thymus weight. On the other hand, the antibody-forming capacitiy against sheep erythrocytes of dwarf mice was significantly increased even when the treatment with growth hormone was started at 3 months of age. A marked increase in the number of lymphoid cells in dwarf mice was observed by treatment with thyroxin, even if treatment was started either at 7 days or 3 months of age. Similar changes were also obtained in the antibody-forming capacity.     

Relationship between hematopoietic stem differentiation and the functional state of the thymus]

The direction of differentiation of the stem cells with respect to the physiological activity of thymus determined by the age of an animal was studied by means of histological analysis of hemopoietic colonies in the spleen of lethally irradiated mice. The immaturity of thymus of its involution are characterized by the inhibition of differentiation of the stem cell along the granuloid path. An analysis of the data on differentiation of the stem cells in mice of different age, as well as in thymectomized mice allows to draw a conclusion that the process of differentiation of the hemopoietic stem cells is thymus-dependent.     

The annual involution and regeneration of the thymus in hibernating animals and perspectives of its studies in gerontology and stem cell proliferation

Data on a unique phenomenon of annual involution and neogenesis of thymus gland in hibernating animals are reviewed. In accordance with morphological findings, the annual thymus involution in hibernating animals is close to the age-dependent thymus involution occurring in all mammals once in a lifetime. In opposite, thymus involution in hibernating animals is totally different from the accidental involution. During hibernation, the thymus tissue is substituted by the brown fat tissue. In the spring, thymus gland neogenesis stats with intensive growth of epithelial tissue followed by lymphocyte infiltration and exhaustion of brown tissue. Morphological changes in the thymus gland within the annual cycle were compared with seasonal dynamics of structural and functional changes in peripheral lymphoid organs (spleen, lymphoglandular, peritoneal fluid). A general regularity was observed involving a decreased functional activity of immune cells in autumn, its sharp depression during winter hibernation, and obvious increase in summer with the onset of a season of animal activity. It is supposed that a sharp increase in the tumor necrosis factor (TNF) production observed during short-term awakenings in winter may serve an important link in this unique immune adaptation mechanism. The season changes in cellular TNF secretion suggest a mobilization of protective resources in hibernating animals in autumn and winter, i.e. in seasons when the thymus gland activity is depressed. The annual involution of thymus gland cannot be related to droppings in the environmental or body temperatures, as it comes long before their fall. Additionally, it is not related to ageing, as it occurs already in young hibernating animals. The role of hormones, including melatonine and corticosteroids, in mechanisms regulating thymus gland involution in hibernating animals is discussed.     

Trypanosoma cruzi: alteration in the lymphoid compartments following interruption of infection by early acute benznidazole therapy in mice

Disability and mortality as consequence of Chagas disease is enormous in South America. Recently, the success of the trypanocidal treatment with benznidazole, the only available drug, has been associated with the host immune response. In the current study, the impact of benznidazole administration immediately after the experimental infection with Trypanosoma cruzi was evaluated in the main lymphocyte populations in lymphoid organs. Untreated mice displayed enlargement of spleen and lymph node related to the increased frequency of T and B lymphocytes, respectively. An intense thymus involution with the depletion of CD4(+)CD8(+) double-positive thymocytes also occurred. Benznidazole treatment led to a partial reversion of the spleen and lymph node enlargement related to changes in the frequency of lymphocyte subsets due to infection. Prevention of thymus involution was achieved, with the profile of thymocyte subsets similar to that of non-infected mice. The parasitic load at the onset of T. cruzi infection seems critical to trigger immune system activation.